how do you connect to a Excel database using c#

Hmmm, perhaps I'm mistaken but there are no 'Excel databases.' I think you simply wish to read from an Excel file > that is, a spreadsheet. In which case, there are probably (or rather must be) API's out there and a Google search will definitely aid you in that.

Or perhaps you mean to access a Microsoft Access database?

can we use dataset in console mode and how

You can use one of the Microsoft database connectors, if you have it installed, some may be provided by installing Office or other products. Your DSN string will be something like:

Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyExcel.xls;Extended Properties="Excel 8.0;HDR=Yes;IMEX=1";

at least, if you are using the Jet OLEDB type connection. There are others, see http://www.connectionstrings.com/ for better informed examples.

This will allow you to access a table within a worksheet, the HDR=Yes tells it to expect a row of column names at the top, you have to handle the data types yourself, I think. I have working code examples at work someplace but nothing available here.